As mentally retarded children are mainstreamed into public schools, overcoming the negative attitudes of their new classmates create difficult obstacles to their social integration. The research in this proposal is directed toward determining how the social acceptability of mentally retarded children among their nonretarded peers is affected in laboratory and natural situations by the following factors: a) labels (such as mentally retarded); b) personal characteristics (of mentally retarded children such as academic behavior and physical appearance); and c) perceived similarities (between mentally retarded and nonretarded children). The research also will help determine if the stigmatization of mentally retarded children can be impeded or reversed in laboratory and natural situations by these factors. In three studies, children will respond to a mentally retarded target child presented via videotape or photographs and audiotapes, and/or an actual peer. Utilizing factorial designs, the studies will show how the three factors mentioned above interact to affect children's attitudes in laboratory and natural situations. The research will help educators understand why attitudes toward mentally retarded children are negative and what can be done to improve them.